Method for surface treating plastic products

ABSTRACT

A method for surface treating plastic products is provided. The method includes the steps of providing a plastic substrate, the plastic substrate being made of electroplatable material; forming at least one electroconductive coating on the plastic substrate surface by electro-less plating; forming a copper layer on the electroconductive coating by electroplating; partially etching the surface of the copper layer using a laser to form a rough area; and forming a top coating on the copper layer by electroplating. Both shiny appearance and dusky appearance of the plastic substrate can be present by this method.

BACKGROUND

1. Field of the Invention

The present invention relates to methods for surface treating plastic products, particularly to a method for surface treating plastic products by which the plastic products can present both shiny appearance and dull appearance.

2. Description of Related Art

Various surface decorating technologies are used in manufacturing housings of electronic devices. For example, in order to obtain decorative effect, electroplating or painting is typically employed to treat plastic housings of electronic devices, e.g., mobile telephones, personal digital assistants, or MP3 players. The plastic housings treated by electroplating may be favored by consumers because of their attractive metal appearance and good abrasive resistance.

However, surfaces of the plastic housings treated by electroplating usually only present one of the shiny appearance or dull appearance. Thus, electroplated plastic housings are static in appearance and so are not as attractive as they could be.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In a present embodiment, a method for surface treating plastic products may include following steps.

In a first step, a plastic substrate is provided. The substrate may be made of electroplatable material, such as acrylonitrile-butadiene-styrene (ABS) resin.

In a second step, a pretreatment may be applied to the plastic substrate. During the pretreatment step, the substrate is degreased using an alkali-based cleaning solution to remove any oil stains from its surface. After degreasing, the substrate is etched to roughen the surface. The etching treatment can improve adhesion of the surface of the substrate. During etching treatment, for example, the degreased substrate can be immersed in a heated mixed solution of chromic acid and sulfuric acid. Then, the etched substrate is activated in an acidic colloid solution containing a noble metal compound (e.g., palladium compound).

In a third step, at least one electroconductive coating is formed on the surface of the pretreated substrate by a method of electro-less plating. For example, a copper coating may be deposited on the substrate. It is understood that a nickel coating may be further formed on the copper coating.

In a fourth step, a copper layer is formed on the electroconductive coating by electroplating. The electroplating procedure is carried out, for example, in an bath containing copper sulfate or cupric pyrophosphate.

In a fifth step, the substrate having the copper layer is immersed in a protecting solution containing about 20 to 120 g/l (gram per liter) potassium dichromate for about 1 to 5 minutes. This process protects the electroplated copper layer from oxidation and forming an oxide coating which may reduce adhesion of the copper layer to a subsequent plating coating. It is better to employ an electrolysis process to treat the substrate during the fifth step. The electrolysis process is carried out in the protecting solution using a graphite or carbon board as an anode, the substrate as a cathode, and the protecting solution as an electrolyte, at a current density in an approximate range from 0.5 to 2 A/dm2 (ampere per square decimeter).

In a sixth step, the copper layer is partially etched using a laser to form a rough area. The rough area can be in any form of figures, signs, and characters.

In a seventh step, the substrate is degreased using an alkali-based cleaning solution to remove oil stains and/or other smudginess.

In a eighth step, the substrate is cleaned using a solution containing hydrochloric acid and sulfuric acid to neutralize the residual alkali-based cleaning solution on the substrate.

In a ninth step, a top coating is formed on the copper layer by electroplating. The material of the top coating may be selected from chrome, copper-tin alloy, nickel, zinc and tin.

As mentioned above, because the copper layer forms a rough area, the area of the top coating corresponding to the rough area presents a dusky appearance, and the other portion of the top coating presents a shiny appearance.

It should be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A method for surface treating plastic products comprising: providing a plastic substrate, the plastic substrate being made of electroplatable material; forming at least one electroconductive coating on a surface of the plastic substrate by electro-less plating; forming a copper layer on the electroconductive coating by electroplating; partially etching the copper layer using a laser to form a rough area; and forming a top coating on the copper layer by electroplating.
 2. The method for surface treating plastic products as claimed in claim 1, further comprising dipping the plastic substrate with the copper layer in a protecting solution before etching the copper layer.
 3. The method for surface treating plastic products as claimed in claim 2, wherein the protecting solution contains about 20 to 120 g/l potassium dichromate.
 4. The method for surface treating plastic products as claimed in claim 2, wherein the plastic substrate with the copper layer is immersed in the protecting solution for about 1 to 5 minutes.
 5. The method for surface treating plastic products as claimed in claim 2, further comprising employing an electrolysis process to treat the copper layer using the plastic substrate as a cathode, the protecting solution as the electrolyte while the plastic substrate with the copper layer is immerged in the protecting solution.
 6. The method for surface treating plastic products as claimed in claim 5, wherein the electrolysis process is carried out at a current density in an approximate range from 0.5 to 2 A/dm2.
 7. The method for surface treating plastic products as claimed in claim 2, further comprising a step of degreasing the plastic substrate after etching the copper layer.
 8. The method for surface treating plastic products as claimed in claim 1, wherein the at least one electroconductive coating includes a copper coating.
 9. The method for surface treating plastic products as claimed in claim 8, wherein the at least one electroconductive coating further includes a nickel coating formed on the copper coating.
 10. The method for surface treating plastic products as claimed in claim 1, wherein the top coating is selected from a group consisting of chrome, copper-zinc alloy, nickel, zinc, and tin.
 11. The method for surface treating plastic products as claimed in claim 1, further comprising degreasing, etching, and activating the plastic substrate surface before the electro-less plating. 